Like most innovative modifications made at Corps dams, McNary’s new prototype lamprey-passage structure developed from ideas, drawings and models into its final welded-aluminum form. Testing models May 24-26, 2011, at the Corps’ Engineer Research and Development Center in Vicksburg, Miss., helped Walla Walla District engineers determine which designs would best benefit migrating lampreys while not impacting salmon and steelhead also using the fish ladder.